Valve seat and disc hardfacing
Valve seat and disc hardfacing
(OP)
I have crack problem at seat and disc hardfacing of parallel gate valve size 26 inch .It use F91 and Stellite #6 .I think many valve have the same problem.So I want to change a new valve.What material could we use? Operation temperature is 565 C and pressure is 25 bar.Fluid is steam.





RE: Valve seat and disc hardfacing
RXH
RE: Valve seat and disc hardfacing
RE: Valve seat and disc hardfacing
You can share knowledge but you cant share wisdom. Using knowledge wisely separates engineers from the enthusiastic amateurs that burden our society
RE: Valve seat and disc hardfacing
RE: Valve seat and disc hardfacing
I would guess the problem you have here is not due to materials but the valve design itself. With the advent of changing plant operating philosophies, valves are now heated up and cooled down far more frequently and quickly than previously. This leads to a significant thermal gradient across the crotch area of a Parallel slide valve,(or Wedge gate) often resulting in cracking across the seating area. F91 was meant to overcome this problem as it allowed much thinner sections in this area due to its improved mechanical properties at elevated temperature. Unfortunately many valve companies have copied designs over the years and have not understood the differences between say a WC9 design and an F91 design. They just simply change materials and end up with the same problem.
I believe this is where your problem lies. Try speaking to a UK manufacturer who have modified their designs to suit, Hopkinsons or Dewrance would be a good bet.
RE: Valve seat and disc hardfacing
RE: Valve seat and disc hardfacing
e-mail keeshendriks3@msn.com
RE: Valve seat and disc hardfacing
If you still want a new valve, I'd suggest a WC9/F22 material. This will handle the conditions you mentioned however the valve pressure class could go up and you may end up with a wall mismatch with your existing piping.
Good Luck